MAP2K1 and cardiofaciocutaneous syndrome: Several germline gain-of-function mutations in the RAS/RAF/MEK/ERK pathway are associated with the disease, including KRAS, BRAF, MEK1, and MEK2. CFC syndrome thus belongs to a group of disorders known as RASopathies, which are all caused by pathogenic mutations in various genes encoding components of the RAS pathway.